Reality Check: Orbits and impacts in Avengers #672

The High Evolutionary has some weird ideas. His latest scheme may have been inspired by a real-life doomsday prophecy, that the phantom planet Nibiru will collide with Earth and end all life. For Skepticism Month on AiPT! Comics, we asked astrophysicist and keeper of the Bad Background Science blog, JD Voyek, to explain what they all get wrong about orbital mechanics.

Quick question: what’s in Earth’s orbit on the exact opposite side of the Sun?

Did you answer “Nothing, really”? Brownie points to you.

Did you answer “Counter-Earth”? You’re either a conspiracy theorist or a fan of Marvel comics.

Maybe both…

In Avengers #672 (part of Avengers & Champions: Worlds Collide, available now), we open with two sets of heroes arguing about Counter-Earth’s existence. For those not in the know, it’s a “planet” inhabited by this dude called the High Evolutionary who … evolves stuff.

He made it; that’s all that matters.

Anyway, Nova and Spider-Man claim Counter-Earth’s on exactly the opposite side of the Sun as the Earth is; Hulk and Wasp (correctly) assert it can’t be. As the latter states, “the gravitational pull of a roughly 8,000-mile-wide planet hiding there would noticeably affect the orbits of the other nine planets!”

The Hulk follows up – in only the way a show or comic can, with two people having the same conservation at different locations – with “an unaccounted-for tug of gravity in the solar system would disrupt the trajectory of every Earth satellite in orbit.”

They’re both right, except for the obvious error about the total number of planets (Pluto’s not a planet, guys. That’s right. Fight me.)

The concept of a “counter” Earth goes all the way back to an Ancient Greek philosopher named Philolaus, who believed all objects in the universe orbited some sort of “Central Fire” that wasn’t the Sun, but we couldn’t see it because the world was flat and we were all standing on the wrong side. Counter-Earth, then, was on the other side of the Central Fire, to balance things out.

But now that we know more about physics – and can launch things into space – we know there’s nothing on the other side of the Sun. Its presence would indeed perturb the motions of all the other bodies in the solar system, including our satellites. Given that we’ve sent many a mission to the inner planets and they arrived safe and sound, we know there’s no mysterious extra source of gravity messing things up.

And apparently, unlike in the Marvel Universe, we’ve already launched a spacecraft that got a look at the area. NASA’s STEREO coronagraph probes would have seen Counter-Earth in 2007.

But they didn’t.

Because it doesn’t exist.

Semantics, Mathematics, and Calculating the Apocalypse

In this comic-book universe, a new satellite finally pulls up into the ideal position and sees nothing. Well, for a few moments it does — then a 100-meter wide rock pops out of nowhere and starts heading “directly for Earth” at 275 million miles an hour (aka 123,000 km/s).

It’ll hit in 51 minutes, according to Vision.

But naturally, our heroes stop the giant space potato from destroying the western hemisphere (as Hulk claims it will).

We don’t care about that.

We care about the obvious someone-forgot-to-fact-check science errors.

Like the simple vocab lesson that said space potato wouldn’t be called a “meteor” until it entered Earth’s atmosphere. Vision should have said “meteoroid”.

Or that given that the asteroid appears where Counter-Earth is “supposed” to be, and is heading “directly” for Earth, it’d actually be caught and consumed by the Sun … ’cause … ya know … the whole point of Counter-Earth is that the Sun’s in the way ….

Or that – assuming it could phase through the Sun – traversing 2 AU (1 astronomical unit is, by definition, the distance between the Earth and the Sun) at 275,000,000 mph would take 0.676 hours, or about 40.5 minutes.

(The team arrives at the impact site 49 minutes later … oops ….)

There’s a handy dandy calculator by way of Purdue and Imperial College London for estimating the damage done by a space potato impact. We can enter the diameter, its velocity before hitting the atmosphere, and its approximate density (let’s assume for maximum damage it’s solid iron).

The potato begins to break up at an altitude of 156 km (100 km is considered the edge of space)

The potato bits strike the surface at velocity 105,000 km/s (not 95,000 mph, or about 45.5 km/s, which Vision claims it will)

The impact energy is equivalent to 5.5 billionMegaTons of TNT. It will leave a crater roughly 210 km in diameter and 1.5 km deep.

This is larger than the Chicxulub crater, which is generally associated with the extinction of the (non-avian) dinosaurs. But the damage here is coming (almost) entirely from the potato’s speed. The one that may or may not have led to the destruction of the dinos was, like, 150 times bigger.

The Chicxulub crater was detected by the same thing that caused it — gravity. From USGS

If we rerun the numbers using Vision’s calculation that it will smash into the Earth at 95,000 mph, we still get a lot of damage. Just not as much. Like, a fireball nearly 470 km wide, an earthquake more powerful than anything ever recorded in history, and an airblast that’ll destroy a lot of buildings all by itself.

But not the entire western hemisphere.

So, it’s still a good thing we had some people with physics-defying superpowers around.